Concrete removing composition

ABSTRACT

A composition and method for removing hardened or semi-hardened cementitious substances such as concrete, plaster, mortar, grout and similar substances from surfaces such as exterior and interior building surfaces and exterior surfaces of automobiles. The composition includes anhydrous citric acid as an ingredient together with a thickening or viscosity building agent and a wetting agent. The composition is inherently non-aggressive and environmentally friendly. Therefore, the composition is not hazardous to users and is unlikely to damage surfaces from which the cementitious substance is to be removed.

FIELD OF THE INVENTION

This invention relates to compositions and methods for removing hardenedor semi-hardened cementitious substances such as concrete, paster,grout, mortar and similar substances from surfaces.

BACKGROUND

There is a significant problem, particularly in the constructionindustry, with concrete being inadvertently poured or splashed acrosssurfaces on which is desired that concrete not be applied. When theconcrete is still soft it is relatively easy matter to simply wash awaythe concrete with water. However, frequently concrete splashes occur insituations where the concrete cannot be immediately removed or is notnoticed for some time. In these cases, the concrete hardens and can bevery difficult to remove. Also, removing such hardened concrete cancause damage to the surface from which the concrete is removed.

Similar problems can also occur when plastering either internal orexternal building surfaces or when working with grout, mortar andsimilar substances.

Known removal compositions and methods include the use of stronginorganic adds which attack concrete when applied directly on to theconcrete and allow the concrete to be removed, for example by beingwashed away with water flowing from a hose.

Such known compositions have significant disadvantages. The majordisadvantage is that the use of strong inorganic acids is unfriendly tothe environment. Although these substances can be very effective inremoving concrete, they produce residual substances which arebiologically toxic and which are therefore undesirable.

The other significant disadvantage with the known compositions is thatthe inorganic, acids are strong acids and pose a significant risk ofdamage of the surface upon which the concrete is disposed. For example,surfaces from which concrete is designed to be removed are usuallysurfaces of buildings including exterior cladding and paint work,windows and window frames. Other surfaces include the exterior surfacesof private vehicles such as automobiles which are parked in the vicinityof a construction site and which get sprayed with concrete inadvertentlyduring a construction operation. These surfaces are obviously sensitiveand are easily damaged by strong acids.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide compositions ormethods for removing cementitious substances which will at least go someway toward overcoming the foregoing disadvantages, or which will atleast provide the public with a useful choice.

Accordingly, in one aspect the Invention may broadly be said to consistin a composition for removing a cementitious substance from a surface,the composition including

citric acid, and

an organic thickening agent.

In a further aspect the invention may broadly be said to consist inmethod for removing a cementitious substance from a surface, the methodcomprising the steps of applying a composition of citric acid and anorganic thickening agent to the concrete, allowing the composition toremain in contact with the concrete until such time as the concrete hasbeen substantially transformed to a state whereby it may be removed fromthe surface, and

removing the transformed concrete from the surface or allowing thetransformed concrete to fall away from the surface.

DESCRIPTION OF PREFERRED EMBODIMENT

The present invention provides a composition and related method forremoving hardened or semi-hardened cementitious substances from asurface. The term cementitious substances is used herein to refer tosubstances that include cement or substances that have the properties ofcement such as concrete, plaster, grout, mortar and similar substancesincluding those that have hydrated lime as an ingredient and/or calciumsulphate.

The composition of the present invention includes a specific organicacid (e.g. anhydrous citric acid) in combination with a organic,preferably vegetable based, viscosity builder which is not affected bythe acid (e.g. Xanthan).

In the process of the present invention, the composition is applied as asolution to the hardened or semi-hardened cementitious substance such asconcrete or plaster. The solution is permitted to work until theconcrete or plaster matrix loses its cohesiveness, that is to say untilthe concrete or plaster matrix has been reduced to its component solidsand calcium citrate. The solution may thus be continuously applied untilall the concrete or plaster on the surface has lost its cohesiveness.The remaining solids and calcium citrate either fall off the surfaceunder the influence of gravity or may be removed from the surface byspring with water for example, or by otherwise removing, for examplescraping, sponging, or mopping.

We have found that the use of anhydrous citric acid has the significantadvantage that the acid is an organic acid and is relatively “gentle”.We have found that there are very few substances which have theproperties of anhydrous citric add and which can still be economicallyused for an application such as the non-hazardous removal of concrete orplaster.

The anhydrous citric acid in use reacts with the hydrated lime used inmany cementitious substances such as concrete as a hardener and createscalcium citrate as the residual end substance. Calcium citrate has theadvantage that it is biologically available and therefore does not harmenvironmental microorganisms.

We have found that a concentration range of approximately 25% to 75%anhydrous citric acid in the composition is broadly effective in use.

In use, The composition is applied by spraying, brushing or spongingonto the cementitious substance such as concrete or plaster that needsto be removed. Frequently, the concrete or plaster is located onsurfaces such as walls or the sides of vehicles, so that the solutionmust be of an appropriate viscosity or “thickness” to prevent it fromimmediately draining away from the wall or surface so that the chemicalreaction has an opportunity to take place. In order to ensure thatbiologically available end substances remain, we have used an organicvegetable based substance as a viscosity builder or thickener. We havefound that Xanthan has the particular advantage that it is not affectedby pH, so can be used with anhydrous civic acid and still retain itsproperties of increasing the viscosity of the solution.

Thickening or viscosity building substances other than Xanthan may beused, but we have found Xanthan to be the most suitable. Othersubstances that may be used include celluloses such as methyl celluloseand caboxymethyl celluloses. These have the disadvantage that they tendto be stable in only a very narrow portion of the pH spectrum.

Another preferred ingredient in the composition is a wetting agent toassist with pension of the concrete or plaster. A number of wettingagents may be used, but those that have low toxicity are preferred. Wehave found that triethanolamine taurylsulphate performs well. Thissubstance is non-toxic and non-hazardous.

Other wetting agents that may be used include copolymer types. Thesesuffer the disadvantage of being more expensive. Other options includesulphestol (sold under the trade mark TEEPOL).

A further ingredient that may be added to the composition is one or morearomatic essential oils, preferably in the amount of approximately0.01%. The addition of such oils gives a slightly pearlised effect tothe composition in use and adds a faint tinge of aroma. These aspectsare both attractive to users of such compositions, particularly ifconcrete needs to be removed from objects such as private vehicles.

Another ingredient in the composition, particularly when cleaningvehicles and other objects having surfaces where aesthetic appearance isvery desirable, may be an optical brightener. This ingredient provides adesirable clean, clear finish.

One example of a suitable composition according to the present inventioncomprises a solution of approximately 60% anhydrous citric acid,approximately 0.01% Xanthan, approximately 0.1% triethanolaminelaurysulphate, and water as the remainder of the solution.

Another example of a suitable composition according to the presentinvention comprises a solution of approximately 60% anhydrous citricacid, approximately 0.01% Xanthan, approximately 0.1% triethanolaminelaurysulphate, approximately 0.01% of one or more aromatic essentialoils and water as the remainder of the solution.

Another example of a suitable composition according to the presentinvention comprises a solution of approximately 60% anhydrous citricacid, approximately 0.01% Xanthan, approximately 0.1% triethanolaminelaurylsulphate, approximately 0.01% of one or more aromatic essentialoils, approximately 0.1% optical brightener and water as the remainderof the solution.

We have found that the above solutions are effective in removinghardened or semi-hardened concrete or plaster from surfaces withoutsignificant damage to the surface itself.

Our tests have established that the above solutions are harmless tosurfaces including painted surfaces, traditional architectural andautomotive coatings, anodised or powder coated surfaces, ceramic andterracotta surfaces, and brick and glazing. The above solutions may beinappropriate for use on marble, limestone and unprotected cementfibreboard, but are otherwise generally non-aggressive.

The non-aggressive properties of the above solutions also have theadvantage of being non-hazardous to persons using the solutions. Forexample, the solutions can be splashed on the skin of an operatorwithout harm and can even be consumed by a human being withoutsignificant harm.

The solutions have the significant advantages that they can be sold instandard plastic containers of varying sizes, it can be safely handledby humans without risk and it can also be safely stored. Biologicallyfriendly end substances are produced by use of the solution to removeconcrete, and Xanthan is a naturally occurring substance.

What is claimed is:
 1. A composition for removing a hardened orsemi-hardened cementitious substance including hydrated lime or calciumsulphate from a surface, the composition including approximately 25% to75% anhydrous citric acid and an organic thickening agent.
 2. Acomposition according to claim 1, comprising approximately 60% anhydrouscitric acid.
 3. A composition according to claim 1, wherein thethickening agent comprises approximately 0.01% of the composition.
 4. Acomposition according to claim 3, wherein the thickening agent comprisesXanthan.
 5. A composition according to claim 1, including approximately0.1% of a wetting agent.
 6. A composition according to claim 1, whereinthe remainder of the composition substantially comprises water.
 7. Acomposition according to claim 1, wherein the composition contains oneor more aromatic essential oils.
 8. A composition according to claim 7,wherein the composition contains approximately 0.01% of one or morearomatic essential oils.
 9. A composition for removing a hardened orsemi-hardened cementitious substance including hydrated lime or calciumsulphate from a surface, the composition consisting essentially of about25% to 75% anhydrous citric acid, and Xanthan as a thickening agent,balance essentially water.
 10. A method for removing a hardened orsemi-hardened cementitious substance including hydrated lime or calciumsulphate from a surface, the method comprising the steps of: applying acomposition of approximately 25% to 75% anhydrous citric acid and anorganic thickening agent to the substance; allowing the composition toremain in contact with the substance until such time as the substancehas been substantially transformed to a state whereby it may be removedfrom the surface; and removing the transformed substance from thesurface or allowing the transformed substance to fall away from thesurface.
 11. A method according to claim 10, wherein the compositioncomprises approximately 60% anhydrous citric acid.
 12. A methodaccording to claim 10, wherein the thickening agent comprisesapproximately 0.01% of the composition.
 13. A method according to claim12, wherein the thickening agent comprises Xanthan.
 14. A methodaccording to claim 10, wherein the composition includes approximately0.1% of a wetting agent.
 15. A method according to claim 10, wherein theremainder of the composition substantially comprises water.
 16. A methodaccording to claim 10, wherein the composition contains one or morearomatic essential oils.
 17. A method according to claim 16, wherein thecomposition contains approximately 0.01% of one or more aromaticessential oils.
 18. A method according to claim 10, wherein removal ofthe transformed material is by flushing, sponging or scraping.
 19. Amethod according to claim 10, wherein said composition consistsessentially of about 25% to 75% anhydrous citric acid and said organicthickening agent is Xanthan, balance essentially water.